1. Field of the Invention
The present invention relates to a braking apparatus for a linear motion guiding apparatus equipped on, for example, a machine tool or industrial robot, that guides an object with high precision.
2. Description of the Prior Art
An example of this type of linear motion guiding apparatus of the prior art is shown in FIG. 1.
As shown in the drawing, this linear motion guiding apparatus has a guiding device composed of a bed in the form of long base member 1 and a table in the form of moving body 2 that moves on base member 1. A plurality of rollers (not shown) are provided in this moving body 2, and these rollers roll along a track (not shown) formed along the lengthwise direction of base member 1.
Overhang 1a is formed on one side of base member 1, and linear scale 4 is provided in this overhang 1a. On the other hand, light emitting element 5a and light receiving element 5b are provided on the side of moving body 2 by means of bracket 2a. A detection device for detecting the position of moving body 2 relative to base member 1 is composed by this linear scale 4, light emitting element 5a and light receiving element 5b.
A linear direct current motor, which composes the linear motion guiding apparatus with the guiding device, is composed of a primary side, equipped with a plurality of armature coils 7 arranged in a row in the lengthwise direction of base member 1 on base member 1, and a secondary side, having a field magnet (not shown) attached to the lower surface of moving body 2 in opposition to each armature coil 7. Each armature coil 7 is adhered to coil substrate 8, and fastened with coil substrate 8 to base member 1 by screws 9.
In addition, the field magnet is magnetized so that a plurality of N and S magnetic poles are alternately arranged in a row in the direction in which moving body 2 moves, namely along the lengthwise direction of base member 1.
In the constitution described above, by supplying electrical power at a prescribed timing to each armature coil 7, thrust is generated between both the primary and secondary sides based on Fleming's left hand rule to move and position moving body 2, integrated into a single unit with the secondary side. The position of moving body 2 is then detected by the detection device described above.
In this linear motion guiding apparatus of the prior art, since the moving portion that is positioned only stops by using magnetic force as the braking force, it is unstable under conditions in which vibrations and so forth are applied from the outside. In addition, in the case the supply of electrical power is interrupted for some reason such as a power outage, braking force does not act at all, thus resulting in the problem of causing a situation in which the moving portion falls when using the linear motion guiding apparatus for an upright shaft (in which the direction of operation is vertical) or a state which approximates such.